1. Field of the Invention
The present invention relates to an electronic component such as a piezoelectric resonator, and more particularly, to an electronic component in which an inner electrode for connection to electrodes provided on a pair of surfaces of the electronic component is provided in a member of the electronic component such as a piezoelectric member.
2. Description of the Related Art
Conventionally, in the production of oscillators and other similar devices, piezoelectric resonators utilizing a thickness shear vibration mode have often been used. In energy-trap type piezoelectric resonators utilizing a thickness shear vibration mode, resonance electrodes are provided on both main surfaces of an elongated rectangular piezoelectric plate. In such piezoelectric resonators, a resonance electrode provided on one main surface thereof is electrically connected to a connecting electrode which extends over an end surface of the piezoelectric plate, reaching the bottom surface so that surface-mounting is easily performed via one of the main surfaces. In some cases, the corners of the connecting electrode are scraped when the piezoelectric resonator is processed. Japanese Unexamined Patent Application Publication No. 8-237066 discloses a piezoelectric resonator, which is shown in the perspective view of FIG. 15, which improves the reliability of connecting electrodes provided on the front and back surfaces.
In a piezoelectric resonator 101, resonance electrodes 103 and 104 are arranged so as to oppose each other at the center of an elongated piezoelectric plate 102 disposed therebetween.
Moreover, end-surface electrodes 105 and 106 are provided on the end surfaces 102a and 102b of the piezoelectric plate 102, respectively. The end-surface electrodes 105 and 106 are electrically connected to the resonance electrodes 103 and 104, respectively. Moreover, protective films 107 and 108 are arranged to cover and protect the end-surface electrodes 105 and 106, respectively. The resonance electrodes 103 and 104 are arranged on the main surfaces of the piezoelectric plate 102 to extend over the protective films 107 and 108, respectively.
Connecting electrodes 109 and 110 are provided on the upper and lower surfaces of the piezoelectric plate 102, and are electrically connected to the end-surface electrodes 106 and 105, respectively. Moreover, as shown in FIG. 15, the connecting electrodes 109 and 110 are provided on the upper and lower surfaces of the piezoelectric plate 102 and also on the upper and lower surfaces of the protective films 107 and 108, respectively.
In the piezoelectric resonator 101, the protective films 107 and 108 cover the end-surface electrodes 105 and 106, respectively. This improves the reliability of the electrical connection between the resonance electrode 103 and the connecting electrode 110 and between the resonance electrode 104 and the connecting electrode 109.
Referring to the manufacture of the piezoelectric resonator 101, electrodes (referred to as completely coated electrodes), which will be formed to define the end-surface electrodes, are disposed on the entire areas of the main surfaces of a piezoelectric block 111 shown in FIG. 16, and the piezoelectric block 111 is polarized in the thickness direction. After the polarization, protective films 112 and 113 are provided on the completely coated electrodes (not shown), respectively. The first mother piezoelectric block 111 manufactured as described above is cut along the dashed lines A in FIG. 16. Thus, the second mother piezoelectric block 114 shown in FIG. 17 is obtained. After this, a mother resonance electrode 115 and a mother connecting electrode 116, are provided on the piezoelectric block 114. Subsequently, the piezoelectric block 114 is cut along the dashed lines B to obtain the piezoelectric resonator 101.
In an energy-trap type piezoelectric resonator utilizing a thickness shear vibration mode, undesirable spurious responses are produced, depending on the size in the longitudinal direction of the piezoelectric plate 102. These undesirable spurious responses increase when the size of the piezoelectric resonator is reduced. The length of the piezoelectric plate 102 must be adjusted so that spurious responses, which are due to the length of the piezoelectric plate 102, are suppressed.
The size in the longitudinal direction of the piezoelectric resonator 101 is determined primarily by the thickness of the piezoelectric block 111 as seen in the above-described method of producing the piezoelectric resonator 101. Accordingly, when the longitudinal size of the piezoelectric plate 102 is changed to suppress the spurious responses, the thickness of the piezoelectric block 111 must also be changed. Thus, the adjustment of the length of the piezoelectric plate 102 is very difficult to perform.
To overcome the above-described problems, preferred embodiments of the present invention provide an electronic component in which the reliability of electrical connection of an electrode provided on the upper surface of a member of the electronic component, such as a piezoelectric member, to an electrode provided on the lower surface of the member is greatly improved. Moreover, the size of the member of the electronic component is easily adjusted while eliminating the problems experienced with the conventional techniques described above.
Preferred embodiments of the present invention provide an energy-trap type piezoelectric resonator in which surface mounting is easily performed onto a mother board at least from one main surface of the resonator, the reliability of the electrical connection between the electrodes provided on the main surfaces is very high, the longitudinal size of the piezoelectric member is easily adjusted, and therefore, undesirable spurious responses are easily eliminated when the size of the resonator is reduced.
According to a preferred embodiment of the present invention, an electronic component includes a member having upper and lower surfaces opposed to each other, a pair of side surfaces opposed to each other, and a pair of end surfaces opposed to each other, the pair of side surfaces extend in the longitudinal direction of the member and are opposed to each other in the width direction of the member, a first electrode provided on the upper surface of the member of the electronic component, a flat plate-shaped first inner electrode layer film which is exposed at the upper surface of the member of the electronic component at a desired region in the width direction so as to be electrically connected to the first electrode, said first inner electrode layer extending from the upper surface to the lower surface, and the first inner electrode layer being exposed at the lower surface at a desired region in the width direction, and a connecting electrode provided on the lower surface of the member of the electronic component and electrically connected to the first inner electrode film.
Preferably, the electronic component further includes a second inner electrode layer arranged opposite to the first inner electrode layer via a layer of the member of the electronic component.
Also, preferably, the first inner electrode film extends in a direction that is substantially perpendicular to the upper surface of the member of the electronic component.
At least one of the first inner electrode layer and the second inner electrode layer is preferably arranged to intersect the upper surface at an angle of less than about 90xc2x0.
According to another preferred embodiment of the present invention, a energy-trap type piezoelectric resonator includes a piezoelectric body having an upper surface, a lower surface, a pair of side surfaces opposed to each other, and a pair of first and second end surfaces opposed to each other, the pair of side surfaces extending in the longitudinal direction of the piezoelectric member and opposing each other in the width direction of the piezoelectric member, first and second resonance electrodes provided on the upper and lower surfaces of the piezoelectric member, respectively, the first resonance electrode extending from an edge defined by the first end surface and the upper surface toward the second end surface, the second resonance electrode extending from an edge defined by the second end surface and the lower surface toward the first end surface, the first and second resonance electrodes being arranged to overlap at the approximate center of the piezoelectric member in the longitudinal direction, a flat plate-shaped inner electrode layer which is exposed at the upper surface in at a desired region in the width direction of the piezoelectric member, the inner electrode layer extending from the upper surface toward the lower surface, the inner electrode layer being exposed at the lower surface at a desired region in the width direction of the piezoelectric member, and electrically connected to the first or second resonance electrode, and a connecting electrode provided on the upper or lower surface of the piezoelectric member and electrically connected to the inner electrode layer.
Preferably, the inner electrode layer includes a first inner electrode layer connected to the first resonance electrode and a second inner electrode layer electrically connected to the second resonance electrode.
Also, preferably, the inner electrode layer is exposed at each of the upper and lower surfaces of the piezoelectric member over the entire width thereof.
The inner electrode layer is preferably exposed at the lower surface of the piezoelectric member over a portion of the width thereof.
Preferably, the inner electrode layer extends in a direction that is substantially perpendicular to the upper and lower surfaces.
The inner electrode layer is preferably arranged to intersect the upper surface of the piezoelectric member at an angle of less than about 90xc2x0.
Preferably, the piezoelectric resonator in accordance with another preferred embodiment of the present invention includes a charge-output inner electrode layer defining a capacitor and arranged to allow for output or taking out of the electric charge from the capacitor is arranged to oppose to the inner electrode layer with a layer of the piezoelectric member therebetween.
Other features, elements, characteristics and advantages of the present invention will become more apparent from the detailed description of preferred embodiments below with reference to the attached drawings.